Question 1
Use bond energies to estimate the enthalpy of formation of HBr(g).
BE(H–H) = 436 kJ/mol
BE(Br–Br) = 192 kJ/mol
BE(H–Br) = 366 kJ/mol
◦ +262 kJ/mol
◦ +104 kJ/mol
◦ +52 kJ/mol
◦ –52 kJ/mol
◦ –104 kJ/mol
Question 2
Use the bond enthalpy data given to estimate the heat released when 25.0 g of acetylene gas, C
2H
2, burns in excess oxygen to yield carbon dioxide and water vapor at 25°C.
BE(C–C) = 347 kJ/mol
BE(C≡C) = 812 kJ/mol
BE(C=O in CO
2) = 799 kJ/mol
BE(C–H) = 414 kJ/mol
BE(O–H) = 460 kJ/mol
BE(O=O) = 498.7 kJ/mol
◦ 16.8 kJ
◦ 364 kJ
◦ 447 kJ
◦ 1180 kJ
◦ 1230 kJ